Comparison of Physicochemical Properties of Nitrogen-enriched Activated Carbons Prepared by Physical and Chemical Activation of Brown Coal

Abstract

Nitrogen-enriched active carbon has been obtained from Polish brown coal from the “Konin” colliery. The process of ammoxidation by a mixture of ammonia and air at the ratio of 1:3 has been performed at two temperatures (300 and 350 °C) at different stages of the production, that is, at that of precursor, char, and active carbon. It has been shown that the stage at which the process of ammoxidation is conducted has profound effect on the amount of nitrogen introduced into the carbon structure. The carbonization and activation (by steam or KOH) of nitrogen-enriched samples leads to significant reduction of the nitrogen content. The final products were microporous active carbons of well-developed surface area varying from 604 to 3181 m2/g and having nitrogen content from 0.4 to 6.5 wt%, showing different acid−base character of the surface.